Photoelectrochemical valorisation of organic waste for the cogeneration of solar fuels and value-added chemicals

Abstract

Rapid industrialisation has resulted in severe greenhouse gas emissions through extensive fossil fuel extraction and an increasing volume of solid waste disposal. This perspective review examines the photoelectrochemical (PEC) valorisation of organic waste as a promising solution for addressing the energy crisis and environmental pollution. The current stage of PEC organic valorisation has yet to meet industrial requirements, hindered by its relatively low efficiency, limited robustness, and poor scalability compared to conventional technologies. A better understanding of the working principle of the PEC reaction mechanism, the properties of state-of-the-art photoelectrodes, and the organic waste pre-treatment process is required to pave the path toward practical implementation. In this perspective review, we demonstrate that the strategies employed in the design of photoanodes, including doping, heterojunction formation, co-catalyst modification, nanostructuring, and crystal facet engineering, have different effects on activity, selectivity, and stability. In addition to the hydrogen evolution reaction, selected organic reduction reactions for the synthesis of value-added chemicals in a PEC cell are also discussed, followed by recent progress on integrated PEC cells and their practical assessment for solar fuel and value-added chemical production. Since stability and scalability are also essential parameters beyond efficiency for assessing the techno-economic feasibility of a PEC organic valorisation system, we additionally addressed stability, scalability and the compatibility of photoelectrodes in organic waste valorisation. Finally, conclusions and future perspectives on feasible strategies for PEC valorisation are discussed. We hope this review will serve as a helpful guide in designing effective, robust, and scalable PEC organic waste valorisation systems, making it a viable technology for real-world applications.